Fuel injected spark ignition engines operate using computer controls that are controlled using bit maps pre-generated for the specific engine model. The bit maps are based on predefined coordinated degrees of adjustment of the control parameters generally experimentally determined using a particular internal combustion engine and then used on other engines of the same model to set the various parameters such as fuel flow rate, and spark timing. These predefined adjustments are contained within the memory of the engine control module computer in a bit map so that the computer, when it receives input of specific conditions, generates corresponding parameter control positions based on these bit maps or look-up tables.
Generally, such controls read the air mass-flow rate, throttle position, and other parameters and co-ordinate the application of fuel based on these quantities, i.e. the airflow into the internal combustion engine and the other parameters. These control systems generate significant throttling losses and do not provide for accurate control of the air fuel ratio under different load and power demand conditions. In these systems the throttle opening is changed by the operator when there is a desired change in power output or engine speed and then the fuel supply rate is adjusted based on the new throttle opening and airflow rate and the then current load and speed conditions, generally the air to fuel ratio is 1/1 in these systems. U.S. Pat. No. 5,450,829 issued Sep. 19, 1995 to Beck describes an electronic control system for a diesel engine wherein the various operating parameters of the engines are monitored and fed into an electronic engine control unit. The engine control unit then determines pilot fuel flow conditions, i.e. amount and timing, to thereby improve the efficiency of the operation by providing the proper amount of pilot fuel for ignition for the then current cylinder conditions, i.e. air fuel ratio, density, etc. within a cylinder. This system uses calculations to determine some of the controlled adjustments and lookup table or bitmaps for others.
The concept of using dual fuel inputs to spark ignited internal combustion engines are known see for example the system shown in the Markley U.S. Pat. No. 4,864,989 issued Sep. 12, 1989. This patent discloses a spark plug with a fuel injection system to inject auxiliary fuel directly into the spark plugs so that the pilot fuel is adjacent to the spark electrodes and can be ignited to thereby ignite a leaner main fuel mixture contained within the combustion cylinder itself.